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The literature
contains a large number of data (Pavlov et al, 1970; Kasumyan, Kazhlaev, 1993,
Mamedov et al., 2009; Shamushaki et al., 2007) on the development of the
olfactory and taste sensitivity to food chemical signals and behavioral search
reactions in ontogeny of sturgeon species. However, information regarding food
behavioral response of ship of Kura population (Acipenser nudiventris Lovetzky)
and its hybrids with other species of sturgeon to various chemical stimuli and
food objects are very limited. Insufficient information regarding the behavior
of the ship sturgeon and other aspects of its biology. Apparently is explained
due to the poor accessibility of the ship for experimental studies because of
the small density of this fish in the natural waters, and

their rare
appearance in last year's at the farm conditions. Ship of Kura population
included in the "Red Book" of Azerbaijan and is fished only for
reproductive purposes. Given the above, the scope of this work was to study the
development in ship ontogeny the of a behavioral food search response evoked by
chemical stimuli, as well as to determine the sensitivity of ship to these
stimuli.

Materials
and methods.

The study was
carried out in 2006-2007 at the Khylly Sturgeon Fish Farm of Azerbaijan.
Objects of study were the larvae and juveniles (aged 8-45 days, 5 months and 10
months after hatching) of ship of belonging to the Kura River population. Fish
were grown up in pools. Body length, weight and age (from hatching) of
experimental fishes are shown in

Table 1.

The number of
experiments which were performed on the each of fish age groups were ranged
from 6 to 8. The water temperature during Behavioral trials were carried out in
experimental two-section aquariums with water flow. The concept of experimental
aquarium as well as the methodology of the behavioral experiments and
evaluation of the intensity of fish behavioral response was described in
details in early publications above (Kasumyan, Kazhlaev, 1989, 1993, Kasimov,
Mamedov, 1990, Mamedov et al., 2009). The solutions of monosodium glutamate -
MSG

(NaOOCCH2CH2CH
(NH2)-COOH) were used as the chemical stimuli.

Concentration of
solutions MSG was expressed in mol / l.

Results
and discussion.

Observing the
behavior of the pre-larvae of ship in the pools showed that the period of their
rest is less than at pre-larvae of Russian sturgeon. Kura ship pre-larvae begin
to show motion activity for 3 days prior to the beginning of active (exogenous)
feeding. At the age of 10-12 days (the first 1-2 days of active feeding), most
of the ship larvae moves along the bottom of the aquarium, some larvae
occasionally quickly rise into the upper layers of the water, and then, after a
short swim, sink to the bottom

again. Injection
into the aquarium MSG solutions in concentration from 10-3 to 1 mol
/l does not cause any changes at the background behavior of the larvae of this
age (Table 1).

Table 1. The
intensity of the food search reactions (in 5-points scale) evoked by solutions
of MSG in different concentrations in ship having different age

Object of
researches

MSG concentration,
mol /l

Length L, mm

Weight P, mg

Age, days.

1

101

102

103

104

20

37

10

0

0

0

0

0

-

27

100

14

1,240,1

1,1±0,1

0,6±0,1

0,3±0,1

0

-

37

310

25

2,9±0,1

1,8±0,1

1,4±0,1

0,9±0,1

0,4±0,1

0

51

820

35

3,240,1

2,3±0,1

1,5±0,1

1,2±0,1

0,9±0,1

0

69

1830

45

3,2±0,1

2,3±0,1

1,6±0,1

1,4±0,2

0,9±0,1

0

120

6750

180

3,2±0,1

2,6±0,1

1,6±0,1

1,6±0,2

0,9±0,1

0

210

28700

300

3,2±0,1

2,9±0,1

1,6±0,1

1,6±0,2

0,9±0,1

0

After the
transition to the full exogenous feeding (age of 14 days) the ship larvae still
actively swam most of the time at the bottom of the aquarium. Acts of catching
of organic particles lying on the bottom of the aquarium by touching with their
barbels has been observed rarely. Introduction to the aquarium of the sodium
glutamate solution in concentration 1 mol / l evokes a obvious behavioral
response ship larvae of this age: 10-20 seconds after beginning of SGM
injection larvae that are near the entrance of the compartment with odour, sink
to the bottom and began to show the characteristic elements of search behavior
-moving along a zigzag trajectories. During the movement along these
trajectories fish touched the bottom surface of aquarium with the ends of the
barbels. Frequency of catching acts and moving activity in individuals
responding to chemical stimulus had increased significantly. The total duration
of the reaction was no more than 5-6 minutes.

The intensity of
behavioral response of ship at the age of 25-27 days to the solution of sodium
glutamate becomes significantly stronger. The characteristic elements of search
behavior - moving along the bottom of the aquarium in circular and S-shaped
loop paths and zigzag trajectories, and a high frequency of acts catching as
well. Such characteristic

elements
demonstrate often the fish that are close to the compartment with the odour ,
as well as in the surrounding areas of the aquarium bottom. Reacting specimens
demonstrate the high motion activity. The most intensive search behavior show
the individuals being in the compartment with the stimulus. In this area the
gathering of fish is formed that vigorously and repeatedly moved in circular
and S-shaped path, making frequent acts of catching. While moving at the search
circular and S-shaped path fish makes yaws - small displacement of the head and
the front part of the body on either side of the main direction of motion. Ship
show low response to solutions of sodium glutamate concentration 10-4
mol / l.

The background
behavior and the search response is not significantly altered in fish on the
next age group (35-40 days). A distinctive feature of the behavioral response
of the fish of this age is more pronounced ability to locate the source of a
chemical signal, a longer time for complete decay of the reaction (5-6
minutes), and the display of search behavior, not only in the area of maximum
concentration, but also on a wider section of the bottom of aquarium.
Behavioral response was observed up to a concentration of a solution of sodium
glutamate 10-4 mol/l.

Behavioral
experiments performed on the juveniles at age of 5 and 10 months shown that the
definitive level of chemical sensitivity of ship at this age is the same as in
much younger fish at the age of 35-40 days -

10-4 mol
/ l.

At the result of
the present study it was found that the chemical sensitivity to food chemical
signals in the ontogeny of the Kura ship occurs immediately after the
transition of young fish to full exogenous feeding. Similar results were
obtained in other species of sturgeon (Kasimov, Mamedov, 1990; Kasumyan,
Kazhlaev, 1989, 1993). In particular, it was found that the ability to respond
to extracts of food organisms occur in the ontogeny of Russian sturgeon
(Acipenser gueldenstaedtii), Siberian sturgeon (Acipenser baerii) and stellate
sturgeon (Acipenser stellatus) after the transition to full exogenous nutrition
in 8-12 days after hatching.

Peculiarities of
the ship reaction and first of all orientation of fish to

odour source
indicates the ability of young ship relying on the perception of food chemical
stimuli, not only to obtain information about the presence of food signal in
the water, but also to search for its source.

The researches
conducted in other species of sturgeon has shown that young sturgeon reaches
definitive level of olfactory sensitivity to food odors by the second month of
their life, about 20 days after appearance of ability to respond to these
signals. It was found that the development of olfactory sensitivity to food
chemical odors in the Russian sturgeon (Acipenser gueldenstaedtii), Siberian
sturgeon (Acipenser baerii) and stellate sturgeon (Acipenser stellatus) ended
when the young fish reaches an age of 35, 38 and 35 days after hatching, with a
body length of 45; 42 and 38 mm and a weight of 650, 520 and 242 mg,
respectively (Kasumyan, Kazhlaev, 1993 Kasimov, 2003, etc.). This process is
completed simultaneously with the formation of the definitive level of
olfactory sensitivity to food chemical signals. This is also demonstrated by a
study of the cytoarchitectonics of olfactory bulb of sturgeons, which shows
that by the age of 35 days the allocation of core cell layers in it completes
(Rustamov, Obukhov, 1986). It was found that the level of definitive olfactory
sensitivity in the aforementioned types of fish to extract of food organisms is
0.0001 g / l. This level of sensitivity is typical for fish with low level of
development of vision ablity, such as, in particular, the sturgeons. In ship
the definitive level of chemical sensitivity to a solution of sodium glutamate
in the age of 35-40 days makes 10-4 mol /l, and further increase of
the sensitivity (aged 5-10 months) does not happen.

The studies found
that the behavioral response to a food chemical signal in the young fishes of
various species of sturgeon occurs on a single stereotype. Absence of any
significant species specific differences in reaction of ship from other
sturgeon species, apparently occurs due to the substantial similarity overall
strategies of sturgeon (Pavlov, Sbikin, 1989), the proximity of functional
development and the role of food search response of distant sensory systems of
distant action.

Data on the time of
formation of the search reactions can be used to adjust the size-age standard
artificially reared sturgeon juveniles released into natural water bodies. The
findings suggest a promising job on creation

of high olfactory
stimulant of feeding behavior for sturgeon, which can be widely used to improve
the attractiveness of the scent of artificial feed.

References

Kasimov R.Yu.
Physiological and ecological justification of terms of release of sturgeon
young fishes from farms in Azerbaijan // Proceedings of the International
Conference "Modern problems of biological resources of the Caspian
Sea." - Baku. - 2003. - P. 23-26. (in russian).

Kasimov R.Yu.,
Mamedov Ch.A. Behavioral responses and possibilities of learning yuveniles of
the South-Caspian Sturgeon population to various substances dissolved in water
and the role of chemosensory systems in their provision // Izv. Akad. Nauk Az.
SSR. Ser. Biol. - 1990. - N. 1. - P. 94-102. (in russian).

4 Department of Fisheries, Faculty of
Natural Resources, University of Tehran, Karadj, Iran

Abstract

The aim of current
study was to find the optimal transition time from live food to artifical food
in pikeperch (Sander
lucioperca) larvae. In
this experiment, pikeperch larvae were fed with seived pond zooplankton and
Artemia nauplii from the first feeding up to day 16 post-hatching (16 dph),
then three weaning times were used on 16 , (W16), 22 (W22), 28 (W28) dph and compared with a
control group (fed on live food only). According to the obtained results, the
best growth (mean weigth gain = 152.78+2.97 mg) and the highest survival rate
(61.85+2.51%) were reported in control group. The lowest weight gain (mean
weigth gain = 28+5.58 mg) and the lowest survival rate (13.33+5.30%) were
observed in larvae weaned at 16 dph. As the larvae fed live food had the best
growth performance it is assumed that the most suitable method for pikeperch
larvae rearing was exclusively with live food, however, the results of growth
performance in larvae weaned at 28 dph was noticeable.

Pikeperch, Sander lucioperca (previously named Stizostedion lucioperca) is a valuable species for aquaculture due
to its rapid growth, flesh quality and high commercial value Hamza et al.
(2008). This species, had been introduced into water reservoirs in several
European countries Larsen and Berg (2008). Pikeperch is found in freshwater and
brackish water in the Caspian watershed (Ural, Volga, Kura and Sefid Roud
rivers) and in the basins of the Black, Azov, Aral, and Baltic Sea Craig (2000)
and it is one of the most valuable fish in the southern part of Caspian Sea and
distributed from the Gorgan Bay to the Anzali Lagoon Abdoli and Naderi (2009).
Pikeperch stocks in the Caspian Sea declined during the past decades because of
over-fishing and destruction of natural spawning sites Ivanov (2000). To
restock this valuable species in the Caspian Sea, the Iranian fisheries
organization annually produces and releases pikeperch fry into the Caspian Sea.
Total fry production of pikeperch increased from 3.9 million in 2000 to more
than 16 million in 2006. (Iranian fisheries organization annual report,
2008).

In Iran, the larval
rearing of pikeperch takes place in the earthen ponds and stocking of ponds
with pikeperch larvae is done when rotifers bloom. In ponds, pikeperch larvae
initially feed on rotifes and when the larvae size increases, feed on copepod
nauplii azimirad (2010). However, production of pikeperch fry using artificial
food is not practised yet.

The weaning time of
pikeperch larvae has been investigated in several studies, but different
results were obtained (Xu et al., 2003; Ostaszewska et al. 2005; Hamza et
al.,2007; Kestemont et al., 2007). In one study Kestemont et al. (2007) on
weaning time, the highest final body weight of pikeperch larvae was found in
larvae weaned at 19 dph , while the survival rates of larvae was generally
poor. But a recent study Hamza et al. (2007) reported that pikeperch larvae can
be weaned from 15 dph without significant negative effects on digestive enzymes
or development of digestive tract. However, in their study, the final body
weight of larvae in 36 dph that weaned from 15 dph was very low.

According to
Canavate and Fernandez-Diaz (1999), growth and

survival are
powerful tools understanding the effects of both live food and artificial diet
on first-feeding of fish larvae. Therefore, this study was carried out to
specify the most appropriate weaning time for pikeperch larvae and evaluate the
effects of various weaning times on larvae.

Materials
and Methods

Facilities and Fish

In this experiment,
the larvae used (16 dph) were the offspring of one batch of eggs from semi
artificial spawning with hormonal injection Kucharczyk et al. (2007) wild
females and males caught in the spawning season (lately winter season) in Aras
dam, Urmia, Iran. The brood stocks were transported to the Center of Renewing
Fish Resource Yosefpoor, Siahkal, Iran. After spawning on nest, incubation,
hatching and yolk sac resorption, 6-day old larvae were fed add-libitum a
mixture of sieved zooplankton (mainly rotifers) collected from ponds and
Artemia nauplii at 4 h interval throughout the day from 8 am to 8 pm, then two
thousand four hundred 16 dph were distributed in to the 12 circular tanks (200
larvae per each tank). The flow rate in each tank was approximately 0.5-1 L
min-1 with a slight aeration. Tanks were cleaned by siphoning once a day to
remove the unconsumed food, fish waste and dead larvae Kestemont et al. (2007).

The larvae were
kept in outdoor flow-through water tanks supplied by filtered pond water
(filter size = 50 u). Temperature and dissolved O2, controlled daily, was kept at 19°C and above 6 mg L-1, respectively.
pH was determined twice a week and observed at level 7-8 Szkudlarek and

Zakes (2007).

Experimental Diets

In this experiment,
four different treatments (three weaning times and a control group) were
applied in triplicates (4 x 3 =12 tanks). Three weaning times were applied on
16 (W16), 22 (w22) and 28 (W28) dph. The larval feeding scheme
is summarized in Table 1. A mixture of sieved zooplankton (mainly rotifers) and
newly-hatched Artemia
fransiscana

nauplii were used
as first live foods from 6 to 16 dph and then newly-hatched Artemia nauplii was used alone as live food from 16
dph up to the end of experiment. The commercial diet Bio Optimal (0.5 mm) was
used as the weaning feed to replace the live food. The weaning procedure
consisted of decreasing the proportion of Artemia nauplii while increasing the proportion
of dry feed (Artemia nauplii:dry feed in a ratio of 75:25, 50:50, 25:75 and
0:100%) within 4 consecutive days Kestemont et al. (2007).Control groups were
fed with Artemia nauplii from first feeding to the end of the experiment (34
dph). All groups of larvae were fed at 4 hour interval throughout the day from
4 am to 12 pm manually. Larvae were fed 100% biomass during experiment and
approximately 200-600 Artemia nauplii fish-1 day-1 was
targeted for the control group

Kestemont et al.
(2007).

Table 1: Feeding
regimes followed during the larval rearing of Sander lucioperca

Days (dph)

Control

W16

W22

W28

6-16

Artemia+Rotifera

Artemia+Rotifera

Artemia+Rotifera

Artemia+Rotifera

16-22

Artemia

BioOptimal

Artemia

Artemia

22-28

Artemia

Bioptimal

Bioptimal

Artemia

28-34

Artemia

Bioptimal

Bioptimal

Bioptimal

Sampling procedures

Every 6 day, 10
pikeperch larvae from each replication (30 larvae per treatment) were sampled
and weighed collectively by precision balance (0.1 mg sensitivity) while the
total length individually was measured. The number of dead larvae was recorded
daily. The number of sampled larvae was taken into account for survival. Growth
parameters and survival rate were calculated as follows: formulas:

All statistical
analysis were performed using statistical package SPSS, version 16.0. Data that
expressed as percentages were subjected to arcsine transformation before
statistical analysis. The homogeneity of variances of means was tested by
Levene's test. When data were normally distributed, the mean values for each
parameter of different treatments were analyzed by one-way analysis of variance
(ANOVA). When significant differences among treatments were found (P<0.05),
the means were compared with Duncan's multiple range test.

Results

The growth
performance data and survival reate of sander lucioperca larvae in different trearments are presented in Table 2. Based on
results, the highest weight gain and specific growth rate were observed in
larvae fed only live food during the whole period of rearing (control group).
On the other hands, the lowest weight gain and specific growth rate were found
in larvae weaned at 16 dph. According to the results (Table 2), larvae weaned
on day 28 (W28) showed significantly (P < 0.05) higher weight gain and
specific growth rate compaire to the larvae weaned on 16 (W16) and 22 (W22)
dph. By extending the period of feeding with live food, weight gain, specific
growth rate and avarage daily growth rate of pikeperch were increased. The
highest survival rate was obtained in larvae fed only live food during the
whole period of rearing (Fig. 1). The mean survival rates of larvae weaned on
day 22 and 28 post-hatching

were 19.26±6.09 and
48.89±0.96%, respectively. The highest mortality rate was recorded in larvae
weaned at 16 dph (Table 2).

The determination
of the optimum weaning time of pikeperch larvae is one of the key factors to
the further development of pikeperch

intensive
larviculture Kestemont et al. (2007). Results of the present study showed that
live foods were more efficiently utilized by the pikeperch larvae and larvae
fed only on live food during the whole period of experiment showed the best
growth performance. The higher efficiency of live foods for larvae was
attributed to the presence of digestive enzymes in live foods that help in the
digestion processes (Verreth et al., 1993; Kolkovski et al., 1995).

On the other hand,
the lowest growth and survival were observed in larvae weaned at 16 dph . The
poor response of 16- day old larvae to artificial feed could be related to the
incomplete development of the digestive system and poor effeciency in digestion
and assimilation. A study by Hamza et al. (2007) suggested that pikeperch
larvae can be weaned from 15 dph without significant negative effect on
digestive system (except for alkaline phosphatase). However, it should be
mentioned that in that study, growth performance of larvae weaned at this age
(15 dph) was poor and survival rate was not reported. On the other hand,
Kestemont et al. (2007) reported that the optimal weaning age for pikeperch
larvae was on 19 dph while the survival rate of larvae at this weaning age was
15.3%. They also observed the highest survival rate (24.8%) in larvae fed on
only Artemia nauplii. Survival rate and growth performance of larvae are
powerful tools to evaluate the success of weaning time. If weaning time larvae
is not suitable, it leads to a poor performance in terms of survival and growth
in larvae.

The present study
showed that larvae weaned on 28 dph obtained significantly higher weight gain
and specific growth rate than larvae weaned on 16 and 22 dph. This results
indicate that at this age the acceptance of artificial feed by pikeperch larvae
have been improved and probably digestive capability of pikeperch larvae
developed. This finding is supported by Hamza et al. (2007) who stated that
pikeperch larvae acquire the adult mode of digestion around 29 dph. They
reported the appearance of gastric glands with pepsin secretion and pyloric
caeca at

29 dph.

Generally, the
acceptance of artificial diet by larvae depends on a number of factors, i.e.
suitable size, texture of feed and aroma of feed

Dabrowskii (1984).
In this study, a commercial diet (Bio optimal) with suitable size and good
nutritional quality was used at the weaning time and larvae were fed add-libitum to ensure availability of food to each
larva. Howevere, observation of feeding behaviour of larvae showed that after
adding dry feed to the experimental tanks in weaning times of 16 and 22 dph ,
just some of the larvae attracted to the dry diet and consumed it. Therefore,
the high rate of mortality obsrved in W16 and W22 treatments could be explained
by the poor utilization of artificial feed after weaning. Kestemont et al.
(2007) stated that the high mortality of pikeperch larvae between the ages of
12 and 18 dph was related to the non-feednig phenomen in which larvae were
attracted towards the tank walls and refused feeding.

In conclusion, from
the biological point of veiw, the most suitable method of pikeperch larvae
rearing was only with live food during the whole period experiment (until 34
dph). However, the results of growth performance in larvae weaned at 28 dpg age
was noticeable. In other words, mean weight gain of larave in W28 treatment was
three-forth (75%) of larvae fed only on live food. Therefore, it is possibel to
rear the pikeperch larvae using artificail feed from 28 dph.

1Division of Fisheries, Department of
Natural Resources, 2Department of Food science, College of
Agriculture, Isfahan University of Technology. masiha.ali@gmail.com

Introduction

In the course of
just a few decades, fish farming has developed into a highly productive and
efficient industry to produce animal protein for human consumption. In addition
to good growing conditions, a prerequisite for productivity and economic
sustainability in fish farming can be a reliable supply of effective feeds. For
various reasons, fish meal and fish oil have historically been the dominant raw
materials in the production of fish feeds. Due to the development of more
energy dense feed types as well as general growth of the aquaculture industry,
a significant proportion of the total global fish oil is used for its feed
preparation. A lipid requirement equal to 100% of the world's total fish oil
production is estimated by the year 2010 [24].

While marine oils
are superior in their fatty acids composition they also contain a variety of
toxic compounds including polychlorinated dibenzo-p-dioxins (PCDD),
polychlorinated dibenzofurans (PCDF) and dioxin-like polychlorinated biphenyls
(DL-PCB), particularly the non-ortho and mono-ortho substituted PCBs [14, 15,
17, 18]. These compounds are suspected to be carcinogenic and immunosuppressive
in humans [2, 6, 32]. It is also well-known that lipid oxidation is one of the
major concerns in fish-derived food products. Polyunsaturated fatty acids
(PUFAs) are more easily oxidized than saturated fatty acids (SFAs), and
therefore, food products enhanced with the PUFAs n-3 are also more prone to
lipid oxidation. There is potential human health risks associated with
increased consumption of oxidized PUFAs n-3 products [10, 21].

While it is obvious
that a substitute must be found, replacing fish oil in diets has its own
difficulties as most of the vegetable oils are relatively poor sources of n-3
fatty acids. Exceptions to this are flaxseed and canola oils which are rich in
alpha linolenic acid (18:3n-3) (53% and 12%

respectively) [25].
However, these oils are devoid of longer chain n-3 highly unsaturated fatty
acids (HUFAs n-3) and their inclusion in trout diets results in a significant
decrease in the tissue levels of eicosapentaenoic acid (20:5n-3, EPA) and
docosahexaenoic acid (22:6n-

3, DHA) [3, 4].

Freshwater fish are
capable of converting C18 PUFAs to the longer chain C20 and C22 PUFAs [13]
which are the functionally essential fatty acids in vertebrates [22].

The aim of the
present study was to evaluate the effects of fish oil replacement with canola
oil on nutritive value of fish for human consumption.

Materials
and methods

Rainbow trout
fingerlings with a mean initial body weight of 16.5+0.5 g were purchased from
Cheshmeh Dimeh fish hatchery (Shahre kord, Chaharmahal and Bakhtiari, Iran) and
used in this study.

Three
iso-nitrogenous, iso-calorific and iso-lipidic purified experimental diets were
formulated from 100% fish oil (FO), 100% canola oil (CO) and 1:1 blends of the
oils (FCO). Diets were prepared and stored according to Abery et al., (2002) [1] and De Silva et al.,

(2002) [9].

This study was
conducted indoors in a thermostatically controlled room. Fish were housed in
nine 100 L fiberglass circular rearing tanks in a semi re-circulating system
with an in-line oxygen generator and a physical and biological treatment plant
(flow rate of 6 L min-1). During experiment, fish were kept under a
12-h light: 12-h dark cycle. The experiment was conducted at 13.6+1.3°C, water
quality parameters were measured every second day using Aquamerck test kits
(Merck, Darmstadt, Germany) with a mean pH of 7.3+0.2 and levels of ammonia and
nitrate below 0.1 mg L-1.

270 individually
weighed and measured fingerlings were randomly distributed into the tanks (30
fish per tank) and randomly assigned to one of the 3 different experimental
diets (3 replicates for each experimental diets). Fish were fed twice daily at
approximately 08.30 and 17.00 h to apparent satiation for a period of 56 days.
At the end of the experiment a sample of 18 fish (2 fish per replicate) was
taken and anesthetized in